Method and apparatus for evaluating crimp uniformity



g- 1, 1957 L. P. HOSKINS 3,333,467

METHOD AND APPARATUS FOR EVALUATING CRIMP UNIFORMITY Filed Oct. 50, 1964 2 Sheets-Sheet 1 ZONE 2. ZONE LQELAX/NG ANO RECORD/NO I TENSION/N6 I I 7 24 U f g r I E i 22 E 20 /4 OUT 1 //V TENS/0N OUTPUT RELAX OR SENSING INPUT RELAX OR DRAG OR iEL/JX/NG ROLLS ROLLER TENSION/N6 ROLLs PR5 TENSION/N6 ROLLS u OR/MP k ANGLE 2, R W E L LENGTH l A.

TENS/0N FOROE TENS/0N FORCE LOU/8 P. HOSK/NS INVENTOR.

ATTORNEYS Aug. 1, 1967 L P. HOSKINS 3,

METHOD AND APPARATUS FOR EVALUATING CRIMP UNIFORMITY Filed Oct. 30, 1964 2 Sheets-Sheet 2 PERCENT OF UNCR/MPED LENGTH N FIBER TENS/0N GRAMS PER DEN/ER (6P0) FIG. 3.

LOU/.5 P. HOSK/NS INVENTOR.

BY M

ATTORNEYS United States Patent 3,333,467 Patented Aug. 1, 1967 "ice A'better understanding of my invention may be had from the drawing which forms a part hereof. 3,333,467

METHOD AND APPARATUS FOR EVALUATING CRIMP UNIFORMITY Louis P. Hoskins, Kingsport, Tenn., assignor to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey Filed Oct. 30, 1964, Ser. No. 407,699 4 Claims. (Cl. 73-160) ABSTRACT OF THE DISCLOSURE An evaluation is made of the crimp angle and uniformity of filamentary tow after a pretensioning of the material. The amount of relaxation of tension on a band of crimped tow at a point between its passage through tensioning and relaxing rolls is measured by a force transducer.

My coworker Smith in U.S. 2,790,208 disclosed the use of a reciprocating striker to provide .an additional increment of tension intermittently to tow while under tension provided by passage between retarded and driven rolls. My coworker Jackson in an earlier filed patent, U.S. 2,926,392, disclosed the use of a pair of positively driven dOVWJStI'fiHIIl tension rolls for exerting a pulling force on longitudinally moving tow of crimped continuous filaments after the tow has passed through the nip formed between a pair of upstream rolls retarded so as to exert a holding-back effect on the tow against the pulling force of the tension rolls. According to the teaching of both of these patents the tension on the tow is released in a relaxing zone immediately following the tension rolls. While such apparatus for tensioning and relaxing tow after crimping have been highly successful in the fiber conditioning field, as explained above, as yet there has not been developed a simple and economical method for the reliable measuring of crimp angle.

Crimp angle and crimps per inch afiect the carding, drawing and bulkiness of fiber. These parameters must be controlled if a uniform product is to be produced.

It is therefore apparent that a rapid and economical method and apparatus for measuring crimp angle and amount of crimp during the tow conditioning operation represents a highly desirable result.

One object of this invention is to provide a method and apparatus for measuring the amount of crimp in a sample of tow, yarn, or the like textile product. Another object is to provide an apparatus and methodfor continuously indicating the average crimp angle and crimp variability of crimped, continuous-filament yarn or-tow; A still 'further object is to provide method and apparatus which will give a constant quantitative record of crimp angle and crimps per inch of a moving tow or yarn of synthetic filaments. Further objects will appear hereinafter.

In its broader aspects my invention involves measuring the amount of relaxation of tension on a band of crimped tow at a point between its passage through tensioning rolls and relaxing rolls. The tow passes over a free-turning tension-sensing roller connected by way of a force transducer to a suitable recording device. The tensioning rolls (input relax rolls) turn at any convenient speed which is usually determined by the nature of the process which may occur before or after the apparatus of the invention. The relaxing rolls (output relax rolls) turn at a constant surface speed which is less than that of the tension rolls. Thus, the crimp in the tow recovers sufliciently to maintain a tension in the tow which is proportional to the crimp angle, crimps per inch, modulus of elasticity and surface speed ratio of tensioning rolls and relaxing rolls.

In the drawing:

FIG. 1 is a diagrammatic representation of the crimpmeasuring process of the invention.

FIG. 2 is a schematic illustration of a section of crimped filament in a free, unstressed state (A) and in a tension state (B).

FIG. 3 is a graph which illustrates (in curve A) the relationship between fiilament length and filament tension for a representative filament having a saw-tooth shaped crimp, (in curve B) the same relationship for a filament having larger crimp angle and/or fewer crimps and (in curve C) a similar relationship for a filament with smaller crimp angle and/ or more crimps.

Crimped tow or yarn 10 is fed at relatively low tension to a pair of non-driven pretensioning rolls 12, then through a second pair of constant-speed tensioning rolls 14, then over a free-turning tension-sensing roller 16, next through a pair of relaxing rolls 18 which turn at a constant surface speed substantially less than the surface speed of rolls 14, and finally away from rolls 1 8 to a further processing operation.

The function of pretensioning rolls 12 is to bring the tow in the zone between roll pair 12 and roll pair 14 to a uniform tension high enough to substantially straighten the crimp bends but not high enough to cause permanent deformation of crimp bends. In other Words, the stress in the filaments at the straightened crimp bends is below the elastic limit of the filaments. Rolls 14 are driven at a constant speed to match the mass flow rate of tow or yarn for the process. The tow or yarn is deflected in its path as it passes over the tension-sensing roller 16 in order that a force component proportional to the tow tension will be exerted upon the roller. Since rolls 18 are turning at a lower surface speed than rolls 14, the crimp in the tow recovers and in so doing maintains a tension in the tow which is proportional to the crimp angle, crimps per inch, modulus of elasticity of the fiber and surface speed ratio of rolls 14 and rolls 18. The force on roller 16 istransmitted through appropriate linkage 20 to a force transducer 22, which is connected to a suitable recording instrument 24.

A more detailed description of how tensioning and re laxing and related rolls may be operated is to be found in abovementioned J. W. Smith U.S. Patent 2,790,208.

While curves for filaments of diiferent crimp geometry might have different origins at the zero tension ordinate of FIG. 3, curves for all filaments would approach thepercent uncrimped length as an upper limit. The advantage of using a relativelyhigh pretension between rolls 12 and rolls 14 for the invention is that all filaments can be brought very closely to a known length prior to the controlled relaxation step between rolls 14 and rolls 18.

Thetow tension in the tension relaxation zone between rolls 14 and rolls 18 increases with decreasing crimp angle and increasing crimps per uncrimped length and decreases with increasing crimp angle can decreasing crimps per uncrimped length.

7 The following examples will serve to further illustrate the invention.

Example I The machine used in this example consisted of three pairs of air-loaded rolls, a tension-sensing roll or monitor and tension recording equipment. In this example the pretensioning rolls are referred to as drag rolls, the tension- 5 ing rolls as driven input relax rolls and the relaxing rolls as output relax rolls. Referring to FIG. 1, the tow is straightened in Zone 1 by action of the drag rolls pulling TABLE I Thickness of Test Pillow l Relax Tension, Variation in Crimps per Crimp Angle (cm.) Crimper (lbs.) Relax Tension, Inch 2 eg.) Remarks 1 percent At 0.01 p.s.i. At 0.15 p.s.i.

A 0.3 200 8.2 20.5 12.3 Crimp extremely variable. B 0. 7 45 8. 3 20. 9 12. 9 Crimp moderately variable.

1 Pillows were made by stutfing 23 ounces of carded fiber into standard x 28" finished-size pillow ticks. and thickness measurements were made with a 12%-diameter disc with pressure as indicated.

2 Laboratory measurements and observations.

This example illustrates the ability of the process and apparatus of this invention to detect and measure crimp variability which in turn correlates with bulkiness of the fiber as used in such items as pillows. That is, Sample B tow produced thicker pillows because a greater proportion of the fibers from this tow was crimped Within the optimum range of crimp angle and crimps per inch as indicated by the lower variability in relax tension of 45% as compared to 200% for Sample A tow.

Example 11 The same conditions as those of Example I were used in the work described in this example except that the relax ratio was 12.5 percent and the surface speeds of rolls 14 and 18 were 125 and 109.4 respectively. The following samples were identical except that the crimper temperature and pressure were varied to change the crimp angle and crimps per inch respectively.

1 Percent re1ax= 100 X back against a pair of driven input relax rolls to a pair of output relax rolls. In Zone 2 the tow is relaxed a predetermined amount and, by bearing upward against a movable, tension-sensing, idler roller, transmits a force through an arm on the opposite end of the roller shaft to a Brush transducer. This transmitted force is proportional to the tow recovery force. The Brush instrument continuously records the recovery force on a chart calibrated in pounds. After leaving Zone 2, the tow passes on to the next operation. The monitor has been found to be responsive to the variations occurring in approximately one-foot lengths of tow. This requires a recorder frequency response of at least about 10 cycles per second.

The following conditions were adopted as standard for this example: 7

(1) Drag roll air pressure, lbs/in. 20 (2) Input and output relax roll air pressures,

lbs/in. 30 40 (3) Percent relax 1 16.7

TABLE II Thickness of Test Pillow (cm.)

Orimper Condition Relax Tension, Remarks on Visual Appearance of (lbs) Crimp At 0.01 p.s.i At 0.15 p.s.i.

High temp.,high pressure 1. 4 21.1 13. 5 Low crimp angle, high crimps/inch. Med. temp., med. pressure 0.8 20.8 12.3 High crimp angle, low crimps/inch.

Example 111 After establishing standard settings, the monitor was Tests indicated that there is relationship between crimp amplitude and tendency of crimped tow to contract after being released from tension. Crimp amplitude is an important factor in obtaining good filling power. A continuous monitoring was used based on these relationships. The system was designed to continuously measure the recovery force of 400,000 denier tow when released from a tension of 20 to 30 pounds. The objective of this example is to correlate tow recovery forces measured by the crimp measuring method and apparatus of this invention with standard pillow tests performed on cut staple used as pillow down or stufling and made from the same sample. The crimp testing device or monitor such as depicted in FIG. 1 was used for this example. The principle of operation is that the recovery force generated by previously tensioned tow varies in a constant percent relax zone according to the type of crimp amplitude that the tow contains (shallow, low amplitude or uniform, normal amplitude, etc.).

operated for several days throughout the processing of several thousand pounds of fiber. Tow and staple samples were collected at intervals throughout the study. The following data were obtained.

(1) Settings used in crimping.

(2) Type of crimper used.

(3) Appearance of crimp on dryer apron.

65 (4) Recovery force as measured by monitor.

denier, L

Percent Average Thickness (cm.) Average Sample Crimper Crimp Recovery Average Amplitude Crimp Number No. Contrac- Force CPI Angle Remarks tion (lbs.) Initial Com- Re- (deg.)

(no load) pressed covered 13 30.0 1. 5 20.9 13.3 18. 3 8. 4 High 90 13 31. 7 1.5 20.9 13.2 18. 2 8.4 90

7 0.9 20.9 13.0 18. 2 8. 1 Generally 85 Crimp angle variable (80120),

high. some Low CPI. 12 27. 9 1. 1 20.9 13.3 18.2 8. 7 85 Crimp angle uniform (80100). 12 28. 6 1.1 20.8 13.0 18.1 8. 7 85 D0. 12 27. 6 1. 0 21. 1 13. 1 18.4 8. 7 d0 85 Do.

7 26. 6 0.8 21. 1 12.9 18. 4 8. 3 Generally 90 CPI variable (7-9), angle variable high. 0-125 4 24. 8 0. 7 21. 1 12. 9 18. 3 8. 0 Low and 90 CPI and angle variable.

4 25. 6 0. 65 20.9 12. 9 18.2 8. 0 d 90 Do. 4 0.3 20. 5 12.3 17. 8 8. 2 90 CPI and angle extremely variable. 4 25.6 0.45 8.2 90 Do. 13 28. 4 0. 7 20.9 12. 9 18.2 8. 3 Variable 85 CPI and angle less variable. 13 27. 7 0.85 21. 2 13.1 18. 6 8.3 High and 85 CPI variable (7.5-8.7), angle varivariable. able (70-100). 13 27. 7 0.8 8. 3 CPI variable (7.5-9.0), angle variable (70l00). l3 0.75 20.9 12.5 18.1 8.3 Do. 13 27. 8 21. 0 12.7 18.4 13 28. 1 0. 9 21.3 13. 3 18.3 8. 8 Generally 80 Crimp very sharp (60-100), CPI

high. variable (7 .5-10) 13 29. 0 1. 2 21. 0 13.0 18.1 8. 7 do 80 Crimp very sharp (60-100), CPI

variable (7-10). 13 30. 4 1.4 20.8 12. 9 18. 0 9. 3 High and 80 Crimp very sharp (60100), CPI

variable. variable (8.5-1 13 28. 5 0. 9 8. 5 do 85 Crimp variable (70120), CPI

variable (7.5-9). 13 29.0 0.95 20.8 12. 9 18. 2 8. 5 do 85 Crimp variable (70120), CPI

variable (7.5-9).

*Tow Stretching Test, Percent Crimp Contracti0n=L L /L X100 Most of the recovery tensions in this example were between 0.5 to 1.0 pound. Percent relax was reduced to less than 16.7% to create a greater recovery force (above one pound). A short run was made at 12.5% relax and it was found that the total recovery force measured by the monitor increased from 1.0 to 1.85 pounds.

The variation of short sections of tow (one foot to sev eral feet) may be studied readily by speeding up the Brush chart from 1250 mm./hour to 5 mm./ second.

The monitor appears to be sensitive at both 12.5% and 16.7% relax to conditions that affect crimp amplitude. Any significant change at the crimper, such as steam pressure, that causes a shift in the amplitude is reflected in the monitor reading.

According to my invention the relax ratio between tensioning and relaxing should be within the range of the available crimp recovery of the tow. As the relax ratio is increased, the force on the measuring roller gradually approaches zero for a given tow. Ratios above the zero force limit may result in an accumulation of excess tow between tensioning and relaxing. It is, however, quite possible for the force on the measuring roller to be zero temporarily if the crimp of the tow is highly variable.

Slippage between tensioning and relaxing rolls may alter the effective relax ratio and result in an erroneous force indication on the measuring roller and accordingly should be avoided. The pressure between paired rolls may be kept high enough to prevent slippage of the tow relative to the rolls. The speed ratio of the rolls may be held constant by no-slipping, connecting drive means such as gears, chain or cog belt drives and the like.

The tension-sensing roller may be made of lightweight material to reduce inertia and mounted on low-friction bearings. The linkage between the tension-sensing roller and the force transducer should also have low inertia and free movement. Such precautions help to increase the sensitivity of the sytsem and allow more detailed analysis of the crimper variation.

The distance between tensioning and relaxing rolls determines the minimum length of tow within which a crimp variation can be detected with best accuracy. Thus, if the distance between tensioning and relaxing rolls is inches and it is desired to detect a variation in crimp angle which exists for only one inch of tow length, the recovery tension in the tow between these rolls would be the average tension over 20 inches of relaxed tow. Therefore, the

effect of even a large crimp variation in a one inch length of tow is quite small. Accordingly a short roll spacing, say 2 inches, would be preferred for detecting crimp variations in a one inch length of tow. With a two inch roll spacing, a variation in one inch length of tow would account for up to 50 percent of the tow under observation at any instant and would result in a relatively large indication on the recorder or indicator. A range of 0.5 inch to 24 inches should be adequate for the distance between the centers of tensioning and relaxing rolls.

While the invention has been described primarily with relationship to its use as a monitor to be used to measure the degree of crimp in a moving filamentary tow during the manufacturing process, it will be readily recognized that it may be used to evaluate crimp uniformity and characteristics for the purpose of checking ball warps or bales of tow used in the Pacific Converter Process or in the manufacture of cigarette filters from baled tow. That is, the tow to be evaluated may come directly from a crimper or other operation in the tow manufacturing process or it may be supplied from a bale or ball warp of tow. The instrument is usable on any chemical composition of filamentary tow such as regenerated viscose, cellulose acetate, acrylic, modacrylic, polyester, polyamide or polyolefin polymers. The type of crimp may be of the sawtooth type, sinusoidal or helical.

While the use of the crimp meter has been illustrated with heavy denier tows, it may also be used when scaled down in size to measure in ounces or grams to evaluate the uniformity of texture or crimp in textured yarns such as described in U.S. Patents 2,439,815, 2,019,185, 3,099,- 064, 2,960,730, in my copending application U.S. Serial No. 826,714 or, in U.S. No. 281,644 of my coworker Chase. When used in connection with these textured crimped yarns, my device is quite useful for monitoring and controlling the uniformity of crimp texture so that knitted or woven fabrics or tufted rugs prepared therefrom are uniform and substantially streak-free in appearance.

From the foregoing description it should be apparent that I have provided simple and economical method and apparatus for testing crimp angle and amount in synthetic-filament tow or yarn.

Further advantages of this invention include:

(1) Inspection of all material produced is obtained.

(2) A permanent record is prepared automatically.

(3) A drop in quality level can be detected immediately and can be rapidly followed by appropriate corrective action. Thus, production of substandard tow can be held to a minimum.

(4) The effectiveness of the corrective action can be immediately measured.

Although the invention has been described in considerable detail with particular reference to certain preferred embodiments thereof, variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

I claim:

1. A method of evaluating crimp in tow which comprises passing a band of moving crimped tow through the nip formed between a pair of tensioning rolls moving counterdirectionally at a substantially constant speed matching that of said moving tow, passing said tow between the nip formed between a pair of relaxing rolls moving counterdirectionally at a substantially constant speed less than that of said tensioning rolls, deflecting said tow between said tensioning rolls and said relaxing rolls by passing it partly around a tension-sensing roller and thereby exerting a force component on the roller proportional to the tow tension, and measuring said force component and thereby indicating the average angle and amount of crimp in said tow.

2. A method of evaluating tow crimp which comprises uniformly pretensioning the crimped tow sufliciently to substantially remove the crimp but not cause permanent deformation thereof, feeding the said pretensioned tow through a first feeding means at a substantially first constant speed, feeding the said tow through a second feeding means at a substantially second constant speed slower than said first speed, and measuring the tension in the tow between said first and second feeding means to obtain an indication of crimp angle and uniformity.

3. In combination with a pair of pretensioning rolls arranged to turn in opposite directions to forward a band of crimped tow and to apply a substantially uniform tension thereto which is sufiiciently high to substantially straighten the crimp in the said tow, a pair of tensioning rolls positioned downstream from said pretensioning rolls and arranged to be driven in opposite directions for receiving said tow from said pretensioning'rolls, said tensioning rolls arranged to be driven at a substantially constant speed substantially equal to that of said tow, and a pair of relaxing rolls disposed downstream from said tensioning rolls arranged to turn in opposite directions at a lower speed than that of said tensioning rolls so as to receive the tow and forward it to processing means, the invention comprising a tension-sensing roller arranged to deflect the tow between said tensioning rolls and said relaxing rolls whereby said tow applies a force component proportional to the tow tension to said roller permitting the crimp in the tow to recover and maintaining a tension in the tow proportional to the crimp angle, crimps per inch, modulus of elasticity of the tow and surface speed ratio of said tensioning and said relaxing rolls, a force transducer connected to said tension-sensing roller, and a recording device connected to said force transducer to register the force component applied to said roller to indicate the crimp in said tow.

4. In combination with apparatus for tensioning and relaxing continuous filament tow comprising respective pairs of tensioning and relaxing rolls, the relaxing rolls being arranged to move at a lower speed than said tensioning rolls to permit the tow crimp to recover, a forcesensing member positioned between said pairs of said tensioning and relaxing rolls, said member being arranged to deflect crimped tow as it moves from said tensioning rolls to said relaxing rolls so as to cause said tow to exert a force upon said member proportional to the tension of the tow as the crimp in the tow recovers, a force transducer connected to said member, and a recording instrument connected to said transducer to measure the force applied to said member to indicate the amount of crimp in said tow.

References Cited UNITED STATES PATENTS DAVID SCHONBERG, Primary Examiner. 

1. A METHOD OF EVALUATING CRIMP IN TOW WHICH COMPRISES PASSING A BAND OF MOVING CRIMPED TOW THROUGH THE NIP FORMED BETWEEN A PAIR OF TENSIONING ROLLS MOVING COUNTERDIRECTIONALLY AT A SUBSTANTIALLY CONSTANT SPEED MATCHING THAT OF SAID MOVING TOW, PASSING SAID TOW BETWEEN THE NIP FORMED BETWEEN A PAIR OF RELAXING ROLLS MOVING COUNTERDIRECTIONALLY AT A SUBSTANTIALLY CONSTANT SPEED LESS THAN THAT OF SAID TENSIONING ROLLS, DEFLECTING SAID TOW BETWEEN SAID TENSIONING ROLLS AND SAID RELAXING ROLLS BY PASSING IT PARTLY AROUND A TENSION-SENSING ROLLER AND THEREBY EXERTING A FORCE COMPONENT ON THE ROLLER PROPORTIONAL OF THE TOW TENSION, AND MEASURING SAID FORCE COMPONENT AND THEREBY INDICATING THE AVERAGE ANGLE AND AMOUNT OF CRIMP IN SAID TOW. 